a whopper of a thread!!! think its taken me nearly 2hrs to read, not sure how much i've digested but its certainly dispelled some myths i'd viewed as facts so thanks on that one!
No where near as far up the thermo-understanding ladder as most of you guys but be able to add my 2 cents to the digressed discussion of measuring ac motor power, there are tools to measure ac power e.g modern flukes with clamp on p.f. meters (almost accurate lol), standard kilowatt hour meters, watt-meter or a combination of normal voltmeters, ammeters, and power factor meters. There are 3 types of AC power, we're interested in 'real power = v x a x p.f' - (the average of the instaneous product of voltage & current), the P=VI furher up the thread is true for d.c pwoer, in a.c. it gives 'apparent power - the product of RMS volts & RMS amps - (iirc if you dont have an RMS meter you can muliply by 0.7071)', finally theres 'reactive power' - (the time average of the instaneous product of voltagte & current with current phase shifted 90 degrees -VAr).
From the specs of the pump you should find a p.f rating. with this you can then use a dvm to measure voltage & current & use 'Real' power = V x A x p.f, not 100% accurate .... although for torque & slip calcs p.f. is assumed as constant, its not!, but its often quoted at particluar / expected duty levels so can be treat as constant, certainly within the bounds of accuracy of the measurement kit i expect to be employed anyway.
p.s not sure of eheim, hydor etc p.f rating but i'd expect for them all to be around 0.8?
p.p.s think i noted someone had a watt meter further up the thread, if they measure true/real power then divide that by apparent power(VA) that will give the power factor for others to use (if not quoted in specs).
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